Jabiru company aircraft wiring is... questionable.
Battery sense should ALWAYS go to the battery (via small fuse) NO MATTER WHAT. anyone who wants an argument, put $10,000 on the table and let's have a bet. Comon, I'll see you in court.
Battery charge should go to the battery to remove alternator 'noise' components from the wiring harness. If the battery charge wire goes to the harness/master, then high frequnecy battery charge current 'noise' will fill and pollute the 12V bus .
Battery charge must go via a fuse (20A in this case) AND ideally, via an isolation relay that is actuated from the master 12V bus.
Battery negative SHOULD go to the negative battery terminal BUT engine block is good enough because starter cable size, direct to battery negative, is usually sufficiently sized to not have any voltage -current noise.
Jabiru factory wiring practice I beleive, may be responsible for Jabiru airframe fires. IE the need of a master battery contactor - because std Jab wiring puts UNFUSED battery B+ through the firewall. Where as good practice, and safe practice, and certainly all part91 cert aircraft, the battery is isolated at the battery via a contactor/relay which is turned on and off via a battery master switch. This has been well covered by me here several times.